Sensor system for ascertaining a torque and for index detection

Abstract

A torque sensor system having an index function and ascertaining a torque between an input shaft and an output shaft connected to each other via a torsion bar, includes: a magnetic unit having a magnetic pole wheel for generating a magnetic field, the magnetic unit being rigidly connected to one of the two shafts; a flux ring unit having a flux ring system for converting and conducting the magnetic flux generated by the magnetic unit, the flux ring unit being rigidly connected to the other shaft; and a sensor unit having at least one first magnetic field-sensitive sensor element for sensing changes in the magnetic flux through the flux ring system, the sensor unit being mounted in a stationary manner relative to the flux ring unit. The index function is implemented with the aid of an index magnet and a further magnetic field-sensitive sensor element.

What is claimed is: 
     
       1. A sensor system for ascertaining a torque between an input shaft and an output shaft connected to each other by a torsion bar, the sensor system comprising:
 a magnetic unit having a magnetic pole wheel configured to generate a magnetic field, the magnetic unit being rigidly connected to one of the input shaft or the output shaft; 
 a flux ring unit having a flux ring system configured to convert and conduct a magnetic flux generated by the magnetic unit, the flux ring unit being rigidly connected to the other of the input shaft or the output shaft; and 
 a sensor unit having at least one first magnetic field-sensitive sensor element configured to detect changes in the magnetic flux through the flux ring system, the sensor unit being mounted in a stationary manner relative to the flux ring unit, the sensor unit having at least one further magnetic field-sensitive sensor element, wherein the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element are situated apart on a circumference in the area of the flux ring system; 
 at least one index magnet mounted on the flux ring unit in the area of the magnetic field generated by the magnetic unit; and 
 an evaluation unit configured to evaluate sensor signals of the first and the further magnetic field-sensitive sensor elements. 
 
     
     
       2. The sensor system as recited in  claim 1 , wherein the flux ring system includes an inner flux ring and an outer flux ring mounted concentrically to the shaft axis and parallel to the magnetic pole wheel, wherein the inner flux ring is provided with ferromagnetic teeth facing outward from the shaft axis in the radial direction and the outer flux ring is provided with ferromagnetic teeth facing inward toward the shaft axis in the radial direction such that the ferromagnetic teeth of the inner and outer flux rings engage with each other. 
     
     
       3. The sensor system as recited in  claim 2 , wherein the sensor unit includes a magnetic flux-collecting element for each flux ring of the flux ring unit, the magnetic flux-collecting elements being situated adjacent to each other on the circumference of the associated flux ring, and wherein the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element are situated in the area of the magnetic flux-collecting elements. 
     
     
       4. The sensor system as recited in  claim 3 , wherein the magnetic flux-collecting elements include a ferromagnetic material and are configured in the form of two concentrically situated ring sections interconnected at least magnetically, an inner ring section being situated on the inside of the associated flux ring and an outer ring section being situated on the outside of the associated flux ring such that each flux ring freely rotates together with an associated one of the input shaft or the output shaft between the inner and outer ring sections of the associated magnetic flux-collecting element, and wherein the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element are situated in the area between the outer ring section of the magnetic flux-collecting element of the inner flux ring and the inner ring section of the magnetic flux-collecting element of the outer flux ring. 
     
     
       5. The sensor system as recited in  claim 4 , wherein at least the outer ring section of the magnetic flux-collecting element of the inner flux ring and the inner ring section of the magnetic flux-collecting element of the outer flux ring have support structures for the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element. 
     
     
       6. The sensor system as recited in  claim 3 , wherein the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element are linear Hall sensors. 
     
     
       7. A method for ascertaining a torque between an input shaft and an output shaft connected to each other by a torsion bar, and for detecting a predefined angle position of the output shaft, the method comprising:
 providing a sensor system including:
 a magnetic unit having a magnetic pole wheel configured to generate a magnetic field, the magnetic unit being rigidly connected to one of the input shaft or the output shaft; 
 a flux ring unit having a flux ring system configured to convert and conduct a magnetic flux generated by the magnetic unit, the flux ring unit being rigidly connected to the other of the input shaft or the output shaft; and 
 a sensor unit having at least one first magnetic field-sensitive sensor element configured to detect changes in the magnetic flux through the flux ring system, the sensor unit being mounted in a stationary manner relative to the flux ring unit, the sensor unit having at least one further magnetic field-sensitive sensor element, wherein the first magnetic field-sensitive sensor element and the further magnetic field-sensitive sensor element are situated apart on a circumference in the area of the flux ring system; 
 at least one index magnet mounted on the flux ring unit in the area of the magnetic field generated by the magnetic unit; and 
 an evaluation unit configured to evaluate sensor signals of the first and the further magnetic field-sensitive sensor elements; 
 
 generating a magnetic flux in the flux ring system rigidly connected to the output shaft, using the magnetic pole wheel rigidly connected to the input shaft; 
 generating a magnetic interference signal within the flux ring system with the aid of the index magnet on the flux ring unit; 
 superimposing the generated interference signal on the magnetic flux of the magnetic pole wheel, wherein the interference signal is detectable within a determined angle position range of the output shaft in predefined measuring locations; 
 detecting, by the sensor unit, a resulting magnetic flux in at least two fixedly predefined measuring locations spaced apart in the area of the flux ring system; and 
 ascertaining, by the evaluation unit, a torque signal and the position of the index magnet from the detected resulting magnetic flux in the at least two fixedly predefined measuring locations.